Apparatus for removing ash from repulped wastepaper

Abstract

An apparatus is disclosed for removing ash from repulped wastepaper which contains ash together with cellulosic fibers. The apparatus includes a frame and a plurality of rolls which are rotatably secured to the frame, such that the axes of rotation of the rolls are spaced and parallel to each other. The plurality of rolls include an upstream roll and a downstream roll having a cylindrical outer surface. A porous belt is supported by and extends around the plurality of rolls to define an endless loop. The belt moves between the upstream and downstream rolls for defining a screening portion. A headbox is disposed within the endless loop, and adjacent to the screening portion for ejecting the repulped wastepaper through the screening portion. A drainage device is disposed on the opposite side of the screening portion relative to the headbox for receiving ash passing through the screening portion. A shower is disposed adjacent to the cylindrical outer surface of the downstream roll for dislodging cellulosic fibers separated from the ash between the headbox and the downstream roll such that the fibers follow the cylindrical outer surface when the belt diverges relative to the outer surface. A doctor is disposed adjacent to the outer surface for doctoring the fibers from the outer surface of the downstream roll. A transverse conveyor is disposed adjacent to the outer surface for conveying the fibers transversely relative to the belt so that the fibers separated from the ash can be subsequently used for forming a reprocessed web.

What is claimed is: 
     
       1. An apparatus for removing ash from repulped wastepaper which contains ash together with cellulosic fibers, said apparatus comprising: a frame;   a plurality of rolls rotatably secured to said frame such that the axes of rotation of said rolls of said plurality of rolls are spaced and parallel relative to each other;   said plurality of rolls including: an upstream roll;   a downstream roll having a cylindrical outer surface;     a porous belt supported by and extending around said plurality of rolls to define and endless loop;   said belt moving between said upstream and downstream rolls for defining a screening portion;   a headbox disposed within said endless loop and adjacent to said screening portion for ejecting the repulped wastepaper through said screening portion;   drainage means disposed on the opposite side of said screening portion relative to said headbox for receiving ash passing through said screening portion;   a shower disposed on the opposite side of said porous belt relative to said cylindrical outer surface for dislodging cellulosic fibers separated from the ash between said headbox and said downstream roll such that the fibers follow said cylindrical outer surface when said belt diverges relative to said outer surface;   a doctor disposed on the opposite side of said porous belt relative to said shower for doctoring the fibers from said outer surface of said downstream roll;   a transverse conveyor disposed adjacent to said outer surface for conveying the fibers transversely relative to said belt so that the fibers separated from the ash can be subsequently used for forming a reprocessed web.   
     
     
       2. An apparatus as set forth in claim 1 wherein said downstream roll has a diameter within the range 40-70 inches. 
     
     
       3. An apparatus as set forth in claim 1 wherein the downstream roll has a diameter within the range 55-65 inches. 
     
     
       4. An apparatus as set forth in claim 1 wherein said headbox is disposed at an angle relative to said screening portion such that the repulped wastepaper is ejected at an angle within the range 40-20 degrees relative to said screening portion. 
     
     
       5. An apparatus as set forth in claim 1 wherein said headbox is disposed at an angle relative to said screening portion such that the repulped wastepaper ejected from said headbox defines an angle within the range 35-25 degrees relative to said screening portion so that fibers within the repulped wastepaper are prevented from flowing through said screening portion while ash and the like passes through said screening portion to said drainage means. 
     
     
       6. An apparatus as set forth in claim 1 in which said drainage means further includes: a save-all pan disposed beneath said screening portion for collecting the ash separated from the repulped wastepaper.   
     
     
       7. An apparatus as set forth in claim 1 wherein said doctor is disposed above said transverse conveyor such that fibers doctored from said outer surface of said downstream roll fall onto said transverse conveyor. 
     
     
       8. An apparatus for removing ash from repulped wastepaper which contains ash together with cellulosic fibers, said apparatus comprising: a frame;   a plurality of rolls rotatably secured to said frame such that the axes of rotation of said rolls of said plurality of rolls are spaced and parallel relative to each other;   said plurality of rolls including: an upstream roll;   a downstream roll having a cylindrical outer surface;     a porous belt supported by and extending around said plurality of rolls to define and endless loop;   said belt moving between said upstream and downstream rolls for defining a screening portion;   a headbox disposed within said endless loop and adjacent to said screening portion for ejecting the repulped wastepaper through said screening portion;   drainage means disposed on the opposite side of said screening portion relative to said headbox for receiving ash passing through said screening portion;   a shower disposed adjacent to said cylindrical outer surface of said downstream roll for dislodging cellulosic fibers separated from the ash between said headbox and said downstream roll such that the fibers follow said cylindrical outer surface when said belt diverges relative to said outer surface;   a doctor disposed adjacent to said outer surface for doctoring the fibers from said outer surface of said downstream roll;   a transverse conveyor disposed adjacent to said outer surface for conveying the fibers transversely relative to said belt so that the fibers separated from the ash can be subsequently used for forming a reprocessed web; and   said drainage means including: a plurality of drainage foils, each foil of said plurality of foils being spaced along the direction of movement of said belt between said headbox and said downstream roll, each of said foils supporting said screening portion and assisting separation of the ash from the fibers.     
     
     
       9. An apparatus as set forth in claim 8 wherein each of said foils extends transversely relative to the direction of movement of said belt. 
     
     
       10. An apparatus for removing ash from repulped wastepaper which contains ash together with cellulosic fibers, said apparatus comprising: a frame;   a plurality of rolls rotatably secured to said frame such that the axes of rotation of said rolls of said plurality of rolls are spaced and parallel relative to each other;   said plurality of rolls including: an upstream roll;   a downstream roll having a cylindrical outer surface;     a porous belt supported by and extending around said plurality of rolls to define and endless loop;   said belt moving between said upstream and downstream rolls for defining a screening portion;   a headbox disposed within said endless loop and adjacent to said screening portion for ejecting the repulped wastepaper through said screening portion;   drainage means disposed on the opposite side of said screening portion relative to said headbox for receiving ash passing through said screening portion;   a shower disposed adjacent to said cylindrical outer surface of said downstream roll for dislodging cellulosic fibers separated from the ash between said headbox and said downstream roll such that the fibers follow said cylindrical outer surface when said belt diverges relative to said outer surface;   a doctor disposed adjacent to said outer surface for doctoring the fibers from said outer surface of said downstream roll;   a transverse conveyor disposed adjacent to said outer surface for conveying the fibers transversely relative to said belt so that the fibers separated from the ash can be subsequently used for forming a reprocessed web;   said drainage means further including: a save-all pan disposed beneath said screening portion for collecting the ash separated from the repulped wastepaper; and     said save-all pan defining a weir;   said weir being disposed between said upstream roll and said headbox such that ash separated from the repulped wastepaper flows in a direction from said headbox towards said downstream roll while water separated from the repulped wastepaper flows over said weir in a direction opposite to the direction of flow of the ash.   
     
     
       11. An apparatus for removing ash from repulped wastepaper which contains ash together with cellulosic fibers, said apparatus comprising: a frame;   a plurality of rolls rotatably secured to said frame such that the axes of rotation of said rolls of said plurality of rolls are spaced and parallel relative to each other;   said plurality of rolls including: an upstream roll;   a downstream roll having a cylindrical outer surface;     a porous belt supported by and extending around said plurality of rolls to define an endless loop;   said belt moving between said upstream and downstream rolls for defining a screening portion;   a headbox disposed within said endless loop and adjacent to said screening portion for ejecting the repulped wastepaper through said screening portion;   drainage means disposed on the opposite side of said screening portion relative to said headbox for receiving ash passing through said screening portion;   said drainage means including: a plurality of drainage foils, each foil of said plurality of foils being spaced along the direction of movement of said belt between said headbox and said downstream roll, each of said foils extending transversely relative to the direction of movement of said belt, each of said foils supporting said screening portion and assisting separation of the ash from the fibers;     a shower disposed adjacent to said cylindrical outer surface of said downstream roll for dislodging cellulosic fibers separated from the ash between said headbox and said downstream roll such that the fibers follow said cylindrical outer surface when said belt diverges relative to said outer surface;   a doctor disposed adjacent to said outer surface for doctoring the fibers from said outer surface of said downstream roll; and   a transverse conveyor disposed adjacent to said outer surface for conveying the fibers transversely relative to said belt so that the fibers separated from the ash can be subsequently used for forming a reprocessed web.   
     
     
       12. A method for removing ash from repulped wastepaper which contains ash together with cellulosic fibers, said method comprising the steps of: supporting a porous belt extending in an endless loop around a plurality of rolls;   moving the belt between an upstream and downstream roll of the plurality of rolls such that the belt between the upstream and downstream roll defines a screening portion;   ejecting the repulped wastepaper from a headbox disposed within the endless loop and adjacent to the screening portion such that the repulped wastepaper is ejected through the screening portion;   receiving ash passing through the screening portion in a drainage device disposed on the opposite side of the screening portion relative to the headbox;   showering a cylindrical outer surface of the downstream roll for dislodging cellulosic fibers separated from the ash between the headbox and the downstream roll such that the fibers follow the cylindrical outer surface when the belt diverges relative to the outer surface, such showering being applied to the side of the belt opposite to the cylindrical outer surface of the downstream roll;   doctoring the fibers from the outer surface of the downstream roll, such doctoring being carried out on the opposite side of the belt relative to the showering of the outer surface; and   conveying the fibers transversely relative to the belt so that the fibers separated from the ash can be subsequently used for forming a reprocessed web.